Amorphous ZnWO4/CuIn4S6.5 with Intrinsic Sulfur Vacancies: Urbach Tail-Modulated Anomalous Charge Transfer toward Efficient Photocatalytic H2 Evolution.

Amorphous semiconductors feature intrinsic lattice disorder and abundant defect states, conventionally regarded as detrimental to photogenerated charge separation and photocatalysis. Nevertheless, lattice symmetry breaking in amorphous systems induces local dipole polarization and prominent Urbach tail band-edge states, providing a unique strategy for carrier regulation. Herein, an amorphous ZnWO4/CuIn4S6.5 heterojunction with intrinsic sulfur vacancies was fabricated via a facile hydrothermal strategy. The synergistic effect of amorphous lattice polarization and sulfur vacancies effectively optimizes the interfacial electronic structure and charge migration behavior. The long-range disordered structure induces dipole moments to modulate the charge transfer pathway, while sulfur vacancies serve as active defect centers to trap photogenerated electrons and suppress charge recombination. By combining systematic spectroscopic and electrochemical tests with DFT calculations, the unique photocatalytic mechanism of the amorphous heterojunction was clarified. The optimized A-ZC 0.6S exhibits a prominent hydrogen evolution rate of 61.70 mmol g-1 h-1, which is 1028 times and 6.0 times higher than those of pristine CuIn4S6.5 and its crystalline counterpart, respectively, with an apparent quantum yield of 8.75% at 365 nm. DFT calculations further confirm that sulfur vacancies significantly optimize the interfacial electronic structure and improve carrier dynamics. This work reveals the synergistic regulation mechanism of amorphous polarization and sulfur-vacancy-induced Urbach tail states, breaking the conventional cognition of the inferior photocatalytic performance of amorphous materials and offering a feasible guideline for the rational design of high-efficiency amorphous photocatalysts.